Why does destructive interference occur when the two pulses overlap instead of constructive interference?

True or false when elements combine to form a mixture, the resulting chemical properties may be very different from those of the elements that make it.

Determine the change in width a, height b, thickness t when a plate is subjected to the uniform distributed load and is made of material having modulus of elasticity e=230 gpa and poisson's ratio ν=1/3. given : a=400 mm and b= 300 mm also the uniformly distributed load in downward y direction of plate is 2 mn/m and in the positive x direction is 3 mn/m and t=20 mm

If you let go of the notebook after lifting it, will it move? how?